This invention relates to centrifugal separators for fluids, and more particularly, to centrifugal pumps of the pitot type having an improved pitot pickup that is particularly resistant to particle erosion.
Centrifugal pumps of the pitot type are well known. Known pitot pumps include those described in the following U.S. Pat. Nos. 3,384,024; 3,776,658; 3,795,459; 3,817,659; 3,838,939; 3,926,534; 3,960,319; 3,977,810; 3,994,618; and 4,036,427. In general, pitot pumps include a drive that drives a hollow casing in rotation within a surrounding fixed housing. A pitot pickup tube in the rotary casing is stationary relative to the casing and intercepts fluid within the casing and draws that fluid from the casing. The exiting fluid has a head larger than its inlet fluid head because of the energy imparted to it by the rotating casing.
Pitot pumps are used for many purposes. One use which illustrates the problem that the present pitot pump solves is to supply motive pressurized fluid to a hydraulic pump located in the bore of an oil well for pumping oil out of the well into a suitable collection facility. In such an application, the motive fluid for the well bore pump can be a portion of the oil produced from the well itself and supplied to the inlet of the pitot pump. Very often, however, the oil taken from the well contains contaminants, such as sand, which should be removed from the oil before the oil is returned under pressure to the pump located in the well. The presence of abrasive solid contaminants such as sand in pressurized oil supplied to the well bore pump can produce undue wear and damage to the pump. For example, solid abrasives can erode journals and journal bearings and destroy seals of such a pump.
Centrifugal pitot pumps, usually in conjunction with other separating equipment, have been used to remove solids from power fluid streams and to separate well fluid into its phases. The pitot tube separator can take power fluid, say oil, from the separator and remove solids from the stream. A pitot tube in the path of the rotating inlet fluid can be subjected to the errosive effect of solids in the fluid. This errosive effect is directly proportional to the cube of the relative velocity between the fluid and the pitot tube. In a casing having a comparatively large radius, in which solids are forced to the periphery of the rotating casing, the separated solids travel at high speeds and the errosive effect caused by impingement of the solids on the pitot pickup can greatly reduce the useful life of the pump.
Accordingly, it is desirable to provide a pitot pump for removing abrasives from an inlet fluid while reducing the errosive effect on the pitot tube caused by the abrasive material impinging on it at high speeds.